This invention relates to a security device for household doors.
The vast majority of front doors for houses are provided with a Yale-type lock and, additionally, in most cases, with mortice-type locks, and, in some cases, extra door-bolt or safety chain devices.
A Yale-type lock is firmly bolted through the door but it latches into a recessed metal casing which is secured to the inside of a door jamb with, usually, three small wood screws.
A mortice-type lock on the other hand weakens the wood of the door or its frame by being let into them giving usually only 6 millimeters of wood cover to the lock. Further, these locks, no matter how expensive and elaborate, are held in position by small light gauge screws, usually four in number, and about 25 millimeters long.
That part of a safety-chain device which is secured to the door is fixed with small screws, usually four of about 12 millimeter length, and that part which is secured to the frame is held in place by only two such screws. That part of a door bolt device (even with a heavy-duty rod or bar of say 16 millimeters diameter) which is secured to the door is fixed in the same way (usually with six screws of 25 millimeters in length) and either bolts into a hole in the frame of the door (which necessarily weakens the frame) or the bolt slides into part of the device secured to the frame which is held, usually, by only two small wood screws.
All these security devices therefore suffer from the same disadvantage, namely that the door can still be forcibly opened, for example with a smart kick or by applying a shoulder to the door.
Other types of security device are in use, mainly for industrial premises, having solid bars of metal or wood which span the door and are sometimes let into the door frame, but these devices are unsightly and, further, they do not permit the door to be moved into a secure ajar position.
The present invention seeks to provide a security device which is not subject to the disadvantages referred to above, which allows the door to be moved into a secure ajar position and which makes forced entry more difficult and/or impossible.